1. Field of the Invention
The present invention relates to a method for placing dummy patterns in a semiconductor device layout. More specifically, the present invention relates to a method for densely arranging dummy patterns between main patterns in accordance with a particular sequence and configuration.
2. Discussion of the Related Art
The development of micro-process techniques has brought about a reduction in semiconductor design rules, thus causing a gradual increase in pattern density and raising importance of accurate pattern formation.
It has become increasingly difficult to realize accurate micropatterning processes, in particular, metal patterning processes. In order to form sophisticated patterns, attempts have been made to solve such difficulties through artificial pattern manipulations such as optical proximity correction (OPC).
In addition, in another attempt to solve such difficulties, a technique wherein dummy patterns are interposed between main patterns has been used. This technique aims to prevent the occurrence of size differences of patterned structures according to the density of the main patterns during a photolithographic and/or etching process.
In subsequent planarization processes, differences in the planarization level of the main patterns may also occur according to the density of the main patterns. This planarization difference can be somewhat solved by interposing dummy patterns between the main patterns.
However, dummy patterns generally use rectangular patterns with a uniform size, which are problematic in that effects thereof are low, when the main patterns are microscopic or dense.
The reason for the problem is that when a uniform size of dummy patterns are arranged in a certain manner, and main patterns are closely arranged or conform to a minimum design rule, it is difficult to insert the dummy patterns close to the main patterns.
FIGS. 1A and 1B are an enlarged image and a scanning electron microscopy (SEM) image of a wafer surface including dummy patterns and main patterns of a general semiconductor device.
FIG. 1A is a view illustrating a state in which micro main patterns are formed in a desired shape. In FIG. 1A, the left image is a micrograph illustrating a magnified image of the wafer surface taken through a microscope and the right image is a SEM illustrating a magnified image of a micro main pattern.
In the left image, long metal lines and micro metal lines are seen, and rectangular dummies which are uniformly spaced apart from one another at the right side thereof are observed.
The right image of FIG. 1A is an SEM image illustrating a micro metal line at magnification. As can be seen from the right image, the micro pattern is suitably formed.
FIG. 1B is a view illustrating a state in which micro main patterns are not formed in a desired shape. In FIG. 1B, a left image is a micrograph illustrating a magnified image of the wafer surface taken through a microscope and a right image is a SEM image illustrating a magnified micro main pattern.
As can be seen from the right image of FIG. 1B, which is an SEM image illustrating a magnified micro metal line, the micro patterns are deformed.
The reason for the pattern deformation is that although being formed, the dummy patterns cannot sufficiently prevent the deformation of isolated micro metal patterns due to excessively large gaps between the main patterns and the dummy patterns. In order to prevent the pattern deformation, it is preferable that dummies be arranged as close to the main patterns as possible. In a case where box-type (e.g., square-shaped) dummies shown in FIGS. 1A and 1B are used, there is a limitation in reducing the distance between main patterns and the dummies through general arrangement methods.